Field
Embodiments described below relate to a semiconductor memory device.
Description of the Related Art
One kind of semiconductor memory device includes a flash memory. In particular, a NAND type flash memory is generally widely used since it is low cost and has a large capacity. Moreover, up to now, many technologies for further increasing the capacity of this NAND type flash memory have been proposed. One such technology is a structure in which memory cells are disposed three-dimensionally. In such a three-dimensional type semiconductor memory device, the memory cells are disposed in a stacking direction, and a conductive layer extends from those memory cells disposed in the stacking direction. Each of the memory cells comprises, between a semiconductor layer acting as a channel and a word line, a memory film that includes a charge accumulation layer.
In such a three-dimensional type semiconductor memory device, it is required that an erase speed in an erase operation is speeded up.